Unlock Bit's Ligers
To unlock Bit's 3 Ligers you must beat Battle Mode with someone from the Bit series.

Unlock Blade Ligers
To unlock the Blade Ligers, Gustav and Giga Gogulous beat Battle Mode with Van or a Zoid from the Zoid series.

Liger Zero Pheonix
Enter the configuration menu and play the following voices in order: 021, 001, 018, 006, 023.

Get special zoids
To get the Blade Ligers, Gustav and Giga Gogulous you must defeat Battle Mode using the Van or Zoid characters. Beat mission mode with one side, then beat it with the other side. Also you can beat Battle Mode with someone from the Bit series to get Bit's 3 Ligers.